var countDecimals = function(num) {
  var len = 0
  try {
    num = Number(num)
    var str = num.toString().toUpperCase()
    if (str.split('E').length === 2) { // scientific notation
      var isDecimal = false
      if (str.split('.').length === 2) {
        str = str.split('.')[1]
        if (parseInt(str.split('E')[0]) !== 0) {
          isDecimal = true
        }
      }
      const x = str.split('E')
      if (isDecimal) {
        len = x[0].length
      }
      len -= parseInt(x[1])
    } else if (str.split('.').length === 2) { // decimal
      if (parseInt(str.split('.')[1]) !== 0) {
        len = str.split('.')[1].length
      }
    }
  } catch (e) {
    throw e
  } finally {
    if (isNaN(len) || len < 0) {
      len = 0
    }
  }
  return len
}

var convertToInt = function(num) {
  num = Number(num)
  var newNum = num
  var times = countDecimals(num)
  var temp_num = num.toString().toUpperCase()
  if (temp_num.split('E').length === 2) {
    newNum = Math.round(num * Math.pow(10, times))
  } else {
    newNum = Number(temp_num.replace('.', ''))
  }
  return newNum
}

var getCorrectResult = function(type, num1, num2, result) {
  var temp_result = 0
  switch (type) {
    case 'add':
      temp_result = num1 + num2
      break
    case 'sub':
      temp_result = num1 - num2
      break
    case 'div':
      temp_result = num1 / num2
      break
    case 'mul':
      temp_result = num1 * num2
      break
  }
  if (Math.abs(result - temp_result) > 1) {
    return temp_result
  }
  return result
}
export default {
  // 加法
  accAdd(num1, num2) {
    num1 = Number(num1)
    num2 = Number(num2)
    var dec1, dec2, times
    try { dec1 = countDecimals(num1) + 1 } catch (e) { dec1 = 0 }
    try { dec2 = countDecimals(num2) + 1 } catch (e) { dec2 = 0 }
    times = Math.pow(10, Math.max(dec1, dec2))
    // var result = (num1 * times + num2 * times) / times;
    var result = (this.accMul(num1, times) + this.accMul(num2, times)) / times
    return getCorrectResult('add', num1, num2, result)
    // return result;
  },
  // 减法
  accSub(num1, num2) {
    num1 = Number(num1)
    num2 = Number(num2)
    var dec1, dec2, times
    try { dec1 = countDecimals(num1) + 1 } catch (e) { dec1 = 0 }
    try { dec2 = countDecimals(num2) + 1 } catch (e) { dec2 = 0 }
    times = Math.pow(10, Math.max(dec1, dec2))
    // var result = Number(((num1 * times - num2 * times) / times);
    var result = Number((this.accMul(num1, times) - this.accMul(num2, times)) / times)
    return getCorrectResult('sub', num1, num2, result)
    // return result;
  },
  // 除法
  accDiv(num1, num2) {
    num1 = Number(num1)
    num2 = Number(num2)
    var t1 = 0
    var t2 = 0
    var dec1; var dec2
    try { t1 = countDecimals(num1) } catch (e) { console.log(1) }
    try { t2 = countDecimals(num2) } catch (e) { console.log(1) }
    dec1 = convertToInt(num1)
    dec2 = convertToInt(num2)
    var result = this.accMul((dec1 / dec2), Math.pow(10, t2 - t1))
    return getCorrectResult('div', num1, num2, result)
    // return result;
  },
  // 乘法
  accMul(num1, num2) {
    num1 = Number(num1)
    num2 = Number(num2)
    var times = 0
    var s1 = num1.toString()
    var s2 = num2.toString()
    try { times += countDecimals(s1) } catch (e) { console.log(1) }
    try { times += countDecimals(s2) } catch (e) { console.log(1) }
    var result = convertToInt(s1) * convertToInt(s2) / Math.pow(10, times)
    return getCorrectResult('mul', num1, num2, result)
    // return result;
  }
}
